Messages in this thread | | | Subject | Re: [PATCH v2] rwsem: Support optimistic spinning | From | Davidlohr Bueso <> | Date | Wed, 30 Apr 2014 09:23:04 -0700 |
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On Wed, 2014-04-30 at 11:14 +0200, Peter Zijlstra wrote: > On Mon, Apr 28, 2014 at 03:09:01PM -0700, Davidlohr Bueso wrote: > > +static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) > > +{ > > + int retval; > > + struct task_struct *owner; > > + > > + rcu_read_lock(); > > + owner = ACCESS_ONCE(sem->owner); > > + > > + /* Spin only if active writer running */ > > + if (owner) > > + retval = owner->on_cpu; > > + else { > > + /* > > + * When the owner is not set, the sem owner may have just > > + * acquired it and not set the owner yet, or the sem has > > + * been released, or reader active. > > + */ > > + retval = false; > > + } > > + rcu_read_unlock(); > > + > > + return retval; > > +} > > Also, the mutex case has a need_resched() test in there; any particular > reason you didn't mirror that?
Good catch. I had made sure we have it in rwsem_optimistic_spin() but overlooked this function, will update.
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